In recent years, along with the progress of miniaturization, increase of frequency and increase of electric current of an electric device and an electronic device, a magnetic body is required to be dealt with similarly. In the current mainstream ferrite materials as a magnetic body, the material properties themselves are approaching the limit, and thus a new magnetic body material is being required. For example, the ferrite materials are replaced with compression molded magnetic materials such as Sendust and amorphous metal, or amorphous foil strip. However, the molding performance of the compression molded magnetic material described above is inferior, and the mechanical strength after baking is low. Further, the production cost of the amorphous foil strip is high due to winding, cutting and formation of gaps. Therefore, the practical application of these magnetic materials is delayed.
In Patent Document 1, it is proposed to provide a method for producing small-sized and inexpensive magnetic core parts having various shapes and characteristics by using a magnetic powder having poor molding performance. Patent Document 1 proposes a method for producing a core part having predetermined magnetic characteristics by injection molding, the method including coating a magnetic powder contained in a resin composition used in the injection molding with an insulation material, and insert-molding either of a compression molded magnetic body and a pressurized powder magnet-molded body in the resin composition, wherein the compression molded magnetic body or the pressurized powder magnet-molded body contains a binder having a melting point lower than the injection molding temperature (see Patent Document 1).
As shapes of the magnetic body which forms the magnetic element, a troidal-shaped magnetic body, a magnetic body having a shape combining an E-shaped magnetic body and an I-shaped magnetic body, a magnetic body having a shape combining U-shaped magnetic bodies, a pot-shaped magnetic body, and a drum-shaped magnetic body are often adopted.
Among the shapes of the magnetic body, in the E-shaped magnetic body, a characteristic as the magnetic element can be adjusted easily due to its easiness of winding, a gap, or the like. While, in the magnetic element using the pot-shaped magnetic body, further miniaturization thereof is possible and excellent silent performance can be obtained because a coil, which is a noise source, is arranged in the magnetic body. Further, a surface of an inductor as the magnetic element is covered by the magnetic body in a pot-shaped inductor, and thereby leakage of magnetic flux to an outside of the inductor can be reduced. The pot-shaped inductor is formed of a magnetic body of soft magnetic material, and a coil, and a bobbin and an insulation case are further used as needed.